Identification of psychometrically strong implementation measures could (1) advance researchers' understanding of how individual characteristics impact implementation processes and outcomes, and (2) promote the success of real-world implementation efforts. The current study advances the work that our team published in 2015 by providing an updated and enhanced systematic review that identifies and evaluates the psychometric properties of implementation measures that assess individual characteristics. A full description of our systematic review methodology, which included three phases, is described in a previously published protocol paper. Phase I focused on data collection and involved search string generation, title and abstract screening, full-text review, construct assignment, and measure forward searches. During Phase II, we completed data extraction (i.e., coding psychometric information). Phase III involved data analysis, where two trained specialists independently rated each measurement tool using our psychometric rating criteria. Our team identified 124 measures of individual characteristics used in mental or behavioral health research, and 123 of those measures were deemed suitable for rating using Psychometric and Pragmatic Evidence Rating Scale. We identified measures of knowledge and beliefs about the intervention (n = 76), self-efficacy (n = 24), individual stage of change (n = 2), individual identification with organization (n = 7), and other personal attributes (n = 15). While psychometric information was unavailable and/or unreported for many measures, information about internal consistency and norms were the most commonly identified psychometric data across all individual characteristics' constructs. Ratings for all psychometric properties predominantly ranged from "poor" to "good." The majority of research that develops, uses, or examines implementation measures that evaluate individual characteristics does not include the psychometric properties of those measures. The development and use of psychometric reporting standards could advance the use of valid and reliable tools within implementation research and practice, thereby enhancing the successful implementation and sustainment of evidence-based practice in community care. Measurement is the foundation for advancing practice in health care and other industries. In the field of implementation science, the state of measurement is only recently being targeted as an area for improvement, given that high-quality measures need to be identified and utilized in implementation work to avoid developing another research to practice gap. For the current study, we utilized the Consolidated Framework for Implementation Research to identify measures related to individual characteristics' constructs, such as knowledge and beliefs about the intervention, self-efficacy, individual identification with the organization, individual stage of change, and other personal attributes. Our review showed that many measures exist for certain constructs (e.g., measures related to assessing providers' attitudes and perceptions about evidence-based practice interventions), while others have very few (e.g., an individual's stage of change). Also, we rated measures for their psychometric strength utilizing an anchored rating system and found that most measures assessing individual characteristics are in need of more research to establish their evidence of quality. It was also clear from our results that frequency of use/citations does not equate to high quality, psychometric strength. Ultimately, the state of the literature has demonstrated that assessing individual characteristics of implementation stakeholders is an area of strong interest in implementation work. It will be important for future research to focus on clearly delineating the psychometric properties of existing measures for saturated constructs, while for the others the emphasis should be on developing new, high-quality measures and make these available to stakeholders.